Cutaneous T cell lymphoma (CTCL) represents a spectrum of disease which currently is not curable by conventional therapy once the disease advances beyond the localized plaque stage. This lack of adequate therapy indicates that new therapeutic and diagnostic approaches should be investigated which can detect this disease earlier and can cure patients when the disease has progressed beyond the local stages. The neoplastic T cells present in CTCL usually express the surface antigens CD3 and CD4, typical of mature T- helper cells, and the CD3-associated T cell antigen receptor (TCR). Studies in this laboratory initially demonstrated that the TCR expresses both a private idiotype, which is a tumor specific marker, and an epitope cross-reactive with normal T cells, which is only slightly less tumor specific than the private idiotype. This project will develop new monoclonal antibodies (mAbs) directed against the TCR expressed on either the actual neoplastic cells, in cases of Sezary syndrome, or cell lines derived from patients with CTCL. The antibodies will be selected for reactivity with the immunogen and a small percentage of normal human T cells. Most of these new mAbs should react with epitopes defined by the different TCR Vbeta or Valpha region genes or gene families. As these mAbs are developed, they will be used in immunofluorescence blocking experiments to confirm that the reagents detect different non-cross blocking epitopes on the TCR. The immunogen used to produce these cross-reactive anti-TCR mAbs will be characterized by a quantitative polymerase chain reaction to determine which V region gene family is expressed by the neoplastic clone. Taken together, these data will characterize the V region specificity of the new mAbs. As more mAbs are developed, they will be used to monitor the blood and bone marrow of patients with CTCL to determine the extent of disease involvement in these tissues and to evaluate whether a stage exists where marrow or blood involvement would preclude bone marrow harvest. Experiments also will be performed using these mAbs to purge normal bone marrow reconstituted with the immunizing cells or concordant cell line. After purging the reactive cells, the remaining marrow cells will be analyzed to demonstrate the depletion of anti-TCR reactive cells and to confirm that hematopoietic colony-forming cells are not depleted. These studies will determine whether transplantation of autologous bone marrow which was purged ex vivo using anti-TCR mAbs could become a clinically useful method to treat these patients. Experience with autologous bone marrow transplants in CTCL patients obtained in our department indicates that these patients can be successfully transplanted and survive the initial stage of leukopenia. Thus, over several years the production of these antibodies would provide a panel of anti-TCR reagents reactive with TCR Valpha and Vbeta gene families which should cover the entire T cell repertoire. One reagent from this panel should react with any individual patient's neoplastic clone and could then be used clinically for diagnostic or therapeutic purposes. Application of these studies to autologous bone marrow transplantation provides a new and potentially curative method to treat not only patients with CTCL but also patients with other T cell neoplasms, such as T-CLL, T cell non-Hodgkin's lymphoma, and some cases of T-ALL, all of which may express the TCR.